Question: Simplify the following expression: $p = \dfrac{y^2 + y - 72}{y + 9} $
Answer: First factor the polynomial in the numerator. $ y^2 + y - 72 = (y + 9)(y - 8) $ So we can rewrite the expression as: $p = \dfrac{(y + 9)(y - 8)}{y + 9} $ We can divide the numerator and denominator by $(y + 9)$ on condition that $y \neq -9$ Therefore $p = y - 8; y \neq -9$